The actual outcomes for the athletes that Just Do It and run like the wind, is nearly unlimited dedication to their sport. Unlimited coaching, training, and actual competing. Not to mention natural inate talent. I say this from having watched and supported our children from grade school through college sports. Having participated in sports as well. All of our family did well, not great, but well. Our son is a B Mountain Biker Racer at the collegite level. He has pros on his team (this is why collegiate mountain biking is not a NCAA sport). His coach was a world champion. His other coach was a New Zealand national champion. Our daughter was a swimmer in high school. She swam in college on the club team, where state champions went because her college did not have a NCAA swim team - Football dominated.
So when some one suggests aw just do it ask did you compete at the varsity level in High School or College? If not, you probably don't know what that phrase really means. If you did, you may have forgotten the endless hours in the pool, or on the track, or getting rained on for hours out on the course - just Trying to Do It.